(1) Field of the Invention
The present invention relates to a polyamide composition. More particularly, the present invention relates to a polyamide composition which has a good fluidity in the molten state and exerts an excellent softness when it is formed into a shaped article. The present invention also relates to an improvement in an electrically conductive polyamide composition comprising a polyamide and electrically conductive carbon black incorporated therein.
(2) Description of the Prior Art
Polyamides per se have a certain softness, but when they are used as thick monofilaments, tubes and hoses, a higher softness is required.
As means for imparting a high softness to polyamides, there have been adopted on an industrial scale a method in which a softening agent such as an aromatic sulfonamide or a p-hydroxybenzoic acid ester is incorporated into polyamides. However, since such known softening agent is liquid, it is difficult to incorporate the softening agent uniformly in a polyamide, and since the compatibility of the softening agent with polyamides is not sufficient, the softening agent exudes to the surface of a shaped article prepared from this polyamide composition, rendering the surface of the shaped article tacky.
It is known that a polyamide can be made electrically conductive by incorporating carbon black at a high content. However, a composition formed by incorporating carbon black at a high content into a polyamide is hard and brittle, and therefore, when a shaped article formed by injection molding of this composition is put out from a mold or while this shaped article is being used, it is readily cracked or broken.
As means for eliminating this defect of a polyamide composition comprising carbon black at a high content, there may be adopted a method in which a softening agent such as mentioned above is incorporated to soften the polyamide composition. Indeed, if such softening agent is incorporated in a large amount, cracking of the shaped article can be prevented. However, since the softening agent is liquid, it is very difficult to incorporate the softening agent in a large amount in the polyamide composition. Furthermore, since the softening agent is poor in the compatibility with polyamides, the softening agent exudes to the surface of the shaped article and renders the surface of the shaped article tacky. Therefore, this method cannot be adopted on an industrial scale.